Pneumatic or hydraulic cylinders have long been used to power or operate numerous types of machinery, including valve actuators. Thrust is generated by virtue of pressure applied against a piston. One means to increase such thrust is to increase the piston size. Such increase in piston size is limited by such parameters as the capabilities of the machine tools and materials used to fabricate the pistons. When the practical limits of such parameters have been reached, multiple cylinders, in tandem arrangement, including a common piston rod, were developed for use. The pressure boundaries of such tandem arrangement of cylinders are the end caps of each cylinder as well as the common wall or end cap dividing adjacent cylinders. Such intermediate cap or wall is generally thin, as a result of design pressure and material strength. As a result, it provided insufficient thickness, on its outer diameter, to install a pressure port adequate for tandem cylinder devices used in many high speed applications. It was to eliminate this increased thickness of the common wall, as well as the accompanying increased length and external piping required, as well as to reduce the size of the external valving and piping, that this invention was directed.